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关键词： cleft palate   retinoic acid   palatal shelves   craniofacial abnormalities   malformations, palatal  

摘要： Malformations of the palate were induced in white rat embryos following maternal exposure to retinoic acid (tretinoin). Five experimental groups and the controls were treated by the following protocol: Group 1: pregnant rats received 100 mg retinoic acid (RA)/kg b.w. suspended in corn oil on gestational day (GD) 11.5;Group 2: 20 mg RA/kg b.w. from GD 8-12;Group 3. 20 mg RA/kg b.w. from GD 7.5-11.5;Group 4. 100 mg RA/kg b.w. on GD 10-11;Group 5: 100 mg RA/kg b.w. on GD 10 and 12;Group 6 received corn oil vehicle from GD 7-14.5;and Group 6: served as non-injected controls. In all retinoic acid treated groups, varying degrees of clefts with occasional attempts of fusion were noted. The severity and frequency of the malformations were dependent on dosage or gestational day of drug treatment. Our results indicate that RA, even at the lowest dose tested (20 mg/kg b.w.) severely affects the various tissues constituting the embryonic palatal shelves by altering cell interaction and possibly programmed cell death. These events would then result in lack of or inadequate differentiation with subsequent formation of aberrant craniofacial architecture.

关键词： 家畜解剖学   CAI课件   肢本设计   组织胚胎学  

摘要： 针对《家畜解剖学及组织胚胎学》课程的特点 ,以该课程中的某个单元为例 。

关键词： temporal sensing   hypoxia   chick embryo   electromagnetic fields  

摘要： We previously studied the response of mammalian cultured cells to weak, 60 Hz-electromagnetic (EM) fields. Two time constants, similar to those observed in chemotaxis, were found to govern the cellular response to the field. We concluded that a system of temporal sensing, similar to that employed in chemotaxis by motile bacteria, was operative. We termed the shorter time (similar to 0.1 s) the "sensing" time, and the longer time (similar to 10 s) the "memory" time. To investigate the possibility that temporal sensing was a general property of EM field-cell interaction, the temporal properties of another EM field-induced effect was studied. The EM field-induced protection against the effects of extreme hypoxia was examined in chick embryos. Embryos were exposed to 60 Hz-magnetic fields, the amplitudes of which were regularly altered throughout the 20-min exposure. Alteration was accomplished either by turning the field off and on at regular intervals (1-50 s), or by introducing brief (10 or 100 ms), zero amplitude gaps, once each second, throughout exposure. When the field was turned on and off at 0.1 s intervals, the protective effect conferred by a constant field was lost. At progressively longer on/off intervals, protection was progressively restored, maximizing at intervals of 10-30 s. Gapping the magnetic field for 10 ms, each second of exposure conferred the same protection as that observed for an uninterrupted field, but gapping the field at 100 ms each second produced a significant reduction in protection. These data exhibit remarkable consistency with those obtained in similar temporal studies of the magnetic field-induced enhancement of ornithine decarboxylase activity in L929 fibroblasts. It appears that temporal sensing is a general feature of the EM field-cell interaction. (C) 2000 Elsevier Science S.A. All rights reserved.

关键词： Xenopus laevis   Spemann organizer   double-stranded RNA   RNA interference   RNAi   antisense RNA   homeobox gene   Xlim-1  

摘要： Double-stranded RNA (dsRNA) interferes with gene expression in various species, a phenomenon known as RNA interference (RNAi). We show here that RNAi is also effective in modifying gene expression in Xenopus embryos. First, expression of an exogenous luciferase gene as a reporter in embryos was reduced by coinjection with dsRNA corresponding to the luciferase gene. Next, injection of dsRNA for Xlim-1, a homeobox gene suggested to be involved in Spemann organizer functions, reduced the endogenous level of Xlim-1 mRNA and produced embryos with reduced eyes or anterior truncation at high efficiency. in addition, injection of an antisense expression construct of Xlim-1 elicited phenotypes very similar to those of Xlim-1 dsRNA-injected embryos. These results indicate the effectiveness of RNAi for loss of function studies in Xenopus embryos, and the importance of Xlim-1 in head formation. (C) 2000 Academic Press.

关键词： 磷酸脂酶C-γ1   人   胚胎组织   免疫细胞化学   表达  

摘要： 采用免疫细胞化学方法探讨了磷酸脂酶 C-γ1(PL C-γ1)在人早期胚胎组织细胞中的表达 ,发现在胚胎龄为 5 2 -76天的多种细胞中均有表达 ,以软骨、软骨膜及肌组织反应最强。结果提示 ,PL C-γ1相关的细胞内信号传递途径对于人早期胚胎细胞的发育、增殖具有重要的生物学意义。

关键词： 人体组织学-实验-医学院校-教材-图谱   人体胚胎学-实验-医学院校-教材-图谱  

关键词： cloning   embryonic stem cells transplantation   ethics   embryo experimentation   law  

摘要： Every day, people die because there are insufficient tissues available for transplantation. The development of cloning and embryonic stem (ES) cell line technologies offers real hope for developing better sources of tissues for transplantation. Moreover, these new technologies may mean that damaged tissue (for example, after a stroke or heart attack) can be replaced with normal functioning tissue rather than scar tissue. Research into 'therapeutic cloning' and the development of ES cell lines is illegal in several States in Australia. It is time to review that legislation in order to allow destructive embryo research. My argument is that at least research should be allowed on spare embryos from assisted reproduction;that it is only one moral view (of several plausible ones) of the status of the embryo which precludes producing embryos for research;that this view is mistaken and so it is morally permissible to produce embryos for research into therapeutic cloning.

关键词： amphibian   axolotl   Ambystoma mexicanum   morphogenesis   GPI-linked proteins   PI-PLC   endoderm   convergent extension  

摘要： Application of phosphatidylinositol-specific phospholipase C to early tailbud stage axolotl embryos reveals that a specific subset of morphogenetic movements requires glycosylphosphatidylinositol (GPI)-linked cell-surface proteins. These include pronephric duct extension, "gill bulge" formation, and embryonic elongation along the anteroposterior axis. The work of Kitchin (1949, T. Exp. Zool. 112, 393-416) led to the conclusion that extension of the notochord provided the motive force driving anteroposterior stretching in axolotl embryos, elongation of other tissues being a passive response. We therefore conjectured that axial mesoderm cells might display the GPI-linked proteins required for elongation of the embryo. However, we show here that removal of most of the neural plate and axial and paraxial mesoderm prior to neural tube closure does not prevent elongation of ventrolateral tissues. Tissue-extirpation and tissue-marking experiments indicate that elongation of the ventral trunk occurs via active, directed tissue rearrangements within the endoderm, directed by signals emanating from the blastopore region. Extension of both dorsal and ventral tissues requires GPI-linked proteins. We conclude that elongation of axolotl embryos requires active cell rearrangements within ventral as well as axial tissues. The fact that both types of elongation are prevented by removal of GPI-linked proteins implies that they share a common molecular mechanism. (C) 2000 Academic Press.

关键词： Fetal Tissue Transplantation   Hematopoietic Stem Cell Transplantation   Stem Cells  

摘要： We report here that neural transplantation of in vitro-differentiated embryonic stem (ES) cells provides a versatile strategy for gene transfer into the central nervous system. ES cells were subjected to an optimized in vitro differentiation protocol to obtain embryoid bodies. These aggregates were stereotaxically transplanted into the brain of recipient adult mice, where they followed a strictly controlled differentiation pattern and eventually formed mature neural grafts. A marker gene, introduced into the ROSA26 locus allowed for precise determination of the fate of the descendants of the transplanted embryoid bodies and revealed that not only neurons but also astrocytes, oligodendrocytes and even microglial cells were graft-derived. Evaluation of long-term experiments showed viable grafts with a stable transgene expression and proved that this approach provides a tool for reliable gene expression within a spatially delimited area of neural tissue.